A concentration of 1×10~6 cells/ml of high viable protoplasts was obtained by using the following optimal concentrations for isolating papaya mesophyll cell protoplasts: 1.0% Macerozyme R-10, 1.5% cellulase Onozuka R-10 and 0.45 mol/L mannitol in the medium (pH5.5). The inoculation was successfully carried out by exposing 5×10~5 cells/ml of the protoplasts to the final mixture of 1 μg/ml PRV-Ys (or Vb) strains and 1μg/ml poly-L-orintine (MW200000). The preliminary results of the studies on behavior kinecti...